Surfactant mixtures

ABSTRACT

Surfactant mixtures which have foamability performance and/or cost advantages over the individual components consist of 5-85% by weight of an amine oxide corresponding to the formula RR&#39;R&#34;NO in which R is a primary alkyl group containing 6-24 carbons and R&#39; and R&#34; are independently selected from methyl, ethyl, and 2-hydroxyethyl and 95-15% by weight of an alkylamidopropyldimethylbetaine in which the alkyl group contains 8-18 carbons. Preferred mixtures are those in which the amine oxide is N-tetradecyldimethylamine oxide and the betaine is cocoamidopropyldimethylbetaine.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of copending application Ser.No. 698,558, filed May. 10, 1991, and now abandoned.

FIELD OF INVENTION

This invention relates to surfactant compositions and more particularlyto such compositions which are mixtures of amine oxides and betaines.

BACKGROUND

It is known that various surfactants have been found to be useful incleaning compositions, such as shower gels, shampoos, and light dutydetergents (e.g., dish detergents)--compositions in which goodfoamability is a prerequisite for consumer approval. The surfactantswhich have been used to the greatest extent in such compositions areanionic surfactants, such as alkyl sulfates, alkyl ether sulfates,sulfonates, sulfosuccinates, and sarcosinates.

Although the use of anionic surfactants in these compositions permitsthe attainment of desirable characteristics, including good foamability,it would be beneficial to find other surfactants which could provideequal or better performance at a lower cost. However, other knownsurfactants, such as amine oxides, betaines, and alkanolamides, areeither more costly than the anionic surfactants or give poorerperformance, e.g., smaller foam volume, when substituted for the anionicsurfactants.

It is sometimes advantageous to use mixtures of surfactants in cleaningcompositions when the surfactants can serve different functions, e.g.,one serving to improve foamability and another serving to adjustviscosity. However, known surfactant mixtures typically provide acompromise between what can be achieved with the surfactant ingredientsalone. Thus, e.g., a mixture of (A) a more costly surfactant whichprovides good foamability by itself with (B) a less expensive surfactantwhich provides poorer foamability by itself will provide an intermediatefoamability.

SUMMARY OF INVENTION

It has been found that a mixture of 5-85% by weight of an amine oxidecorresponding to the formula RR'R"NO in which R is a primary alkyl groupcontaining 6-24 carbons and R' and R" are independently selected frommethyl, ethyl, and 2-hydroxyethyl and 95-15% by weight of analkylamidopropyldimethylbetaine in which the alkyl group contains 8-18carbons provides foamability performance and/or cost advantages over theindividual components of the surfactant mixture.

DETAILED DESCRIPTION

Amine oxides which can be used in the practice of the invention arecompounds corresponding to the formula RR'R"NO in which R is a primaryalkyl group containing 6-24 carbons, preferably 10-18 carbons, and R'and R" are independently selected from methyl, ethyl, and2-hydroxyethyl. The preferred amine oxides are those in which theprimary alkyl group has a straight chain in at least most of themolecules, generally at least 70%, preferably at least 90% of themolecules; and the amine oxides which are especially preferred are thosein which R contains 10-18 carbons and R' and R" are both methyl.

Exemplary of the preferred amine oxides are the N-hexyl-, N-octyl-,N-decyl-, N-dodecyl-, N-tetradecyl-, N-hexadecyl-, N-octadecyl-,N-eicosyl-, N-docosyl-, and N-tetracosyldimethylamine oxides, thecorresponding amine oxides in which one or both of the methyl groups arereplaced with ethyl or 2-hydroxyethyl groups, etc., and mixturesthereof. A particularly preferred amine oxide isN-tetradecyldimethylamine oxide.

Betaines which may be used in admixture with the amine oxides are thealkylamidopropyldimethylbetaines corresponding to the formula ZC(O)NHC₃H₇ (CH₃)₂ NCH₂ COO⁻ which Z is an alkyl group containing 8-18 carbons. Aparticularly preferred betaine is cocoamidopropyldimethylbetaine.

The amine oxide/betaine mixtures of the invention are synergistic, i.e.,provide foam levels higher than can be achieved by the use of eithercomponent alone, when the amine oxide content is anywhere in the rangeof 5-85% by weight. However, greatest foamability is obtained when theamine oxide content of the mixture is about 20-65% by weight. From theaspect of cost effectiveness, i.e., the cost of preparing any givenamount of foam, the preferred mixtures are those containing about 5-75%,more preferably 15-60%, and most preferably 20-50% by weight of theamine oxide.

The invention is advantageous in that it provides novel surfactantmixtures which can provide acceptable levels of foam more economicallythan the individual components of the mixtures. This characteristic ofthe mixtures makes them valuable for use in the cleaning compositionswhich require foaming for customer approval, e.g., shampoos, showergels, and light duty detergents.

When employed in such compositions, the surfactant mixtures are utilizedin an aqueous medium, which typically constitutes about 10-90% of theweight of the compositions; and they may be used in conjunction withother ingredients of the types conventionally used in the compositions.Such ingredients include, e.g., viscosity improvers, pH adjusters,colorants, pearlizing agents, clarifying agents, fragrances,preservatives, antioxidants, chelating agents, skin and hairconditioners, botanical extracts, and antibacterial agents.

The following example is given to illustrate the invention and is notintended as a limitation thereof. Unless otherwise specified, quantitiesmentioned in the example are quantities by weight.

EXAMPLE

Dissolve varying amounts of N-tetradecyldimethylamine oxide andcocoaminopropyldimethylbetaine in hard water (200 ppm as CaCO₃) toprovide solutions having a total surfactant content of 0.1%. Measure thefoamability of the surfactants by (1) placing 30 mL of each of thesolutions in a 100 mL stoppered graduated cylinder, (2) inverting thecylinder ten times, (3) measuring the foam height, (4) repeating steps1-3 twice, and (5) calculating the average of the three measurements.The proportions of amine oxide and betaine used in preparing each of thesolutions and the foam heights obtained from them are shown in the tablebelow.

                  TABLE                                                           ______________________________________                                        % Amine Oxide                                                                              % Betaine Foam Height (mL)                                       ______________________________________                                        100           0        33                                                     85           15        38                                                     75           25        41                                                     65           35        43                                                     60           40        44                                                     50           50        46                                                     25           75        45                                                     20           80        43                                                     15           85        41                                                      5           95        38                                                      0           100       36                                                     ______________________________________                                    

What is claimed is:
 1. A surfactant mixture consisting of 5-85% byweight of an amine oxide corresponding to the formula RR'R"NO in which Ris a primary alkyl group containing 6-24 carbons and R' and R" areindependently selected from the group consisting of methyl, ethyl, and2-hydroxyethyl and 95-15% by weight of analkylamidopropyldimethylbetaine in which the alkyl group contains 8-18carbons.
 2. The surfactant mixture of claim 1 wherein R is a primaryalkyl group containing 10-18 carbons and R' and R" are methyl.
 3. Thesurfactant mixture of claim 2 wherein the amine oxide isN-tetrad-decyldimethylamine oxide and thealkylamidopropyldimethylbetaine is cocoamidopropyldimethylbetaine. 4.The surfactant mixture of claim 1 containing about 5-75% by weight ofthe amine oxide.
 5. The surfactant mixture of claim 4 containing about20-65% by weight of the amine oxide.
 6. The surfactant mixture of claim5 containing about 15-60% by weight of the amine oxide.
 7. Thesurfactant mixture of claim 6 containing about 20-50% by weight of theamine oxide.